Can you explain how apk signature verification works?

Question

Android

I don’t quite understand how checking the app’s authenticity works, so my question is, if after signing the app it creates a file with the checksums of the files, which are then checked, including what prevents the real app from replacing the picture , and then to all the places where you need to make changes corresponding to this picture, eventually getting a modified working apk without a changed signature?

Answer 1

And when the time comes to install / upload to Google Play, the
installer will check the package and compare it with the signature specified in the files
And say that the apk has been changed